This application claims the priority of Japanese Patent Application No. 2000-131984 filed on May 1, 2000, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a control device for an automatic transmission, with which a shift control valve equipped with a manual valve and the like and operating according to the movement of a shift lever by the driver performs switching between a reverse range, neutral range, and drive range, and performs automatic shift control in the reverse and drive ranges.
2. Background of the Invention
With a vehicle equipped with an automatic transmission such as this, the driver moves a shift lever, which actuates a manual valve, which selects the shift range (or shift position), and shift control is automatically carried out within this selected shift range on the basis of the amount of accelerator pedal depression, vehicle speed, and so forth. The shift ranges that can be selected by movement of the shift lever are the park range (P range), reverse range (R range), neutral range (N range), and drive range (such as the D range), with the drive range frequently consisting of a number of ranges, such as the D range, S range, 2 range, and 1 range.
An automatic transmission is designed such that automatic shift control is performed by providing a plurality of solenoid valves, shift valves, and so forth to friction engagement elements (such as clutches) for setting the various gear speeds from the manual valve, and controlling the operation of the shift valves with the solenoid valves, in order to perform shift control automatically on the basis of the amount of accelerator pedal depression, vehicle speed, and so forth within each shift range set by the operation of the manual valve as above. Shift control device structures such as this are disclosed, for example, in Japanese Laid-Open Patent Applications H6-264996 and H9-269062.
With an automatic transmission control device such as this, an oil line going through a solenoid valve, a shift valve, and so forth is switched for every range set by the manual valve, so numerous solenoid valves, shift valves, and the like are needed, which is a problem in that a greater number of parts in the control device tends to lead to higher cost.
In particular, the manual valve switches between the drive and reverse ranges by switching the hydraulic supply oil line going to the drive friction engagement element and the hydraulic supply oil line going to the reverse friction engagement element. Accordingly, the solenoid valve, shift valve, and so forth provided to the hydraulic supply oil line linked to the drive friction engagement element need to be provided separately from the solenoid valve, shift valve, and so forth provided to the hydraulic supply oil line linked to the reverse friction engagement element, which tends to drive up the cost of the control device, and also requires independent control for drive and reverse, making the control more difficult.
It is an object of the present invention to provide a shift control device for an automatic transmission, structured such that the solenoid valve, shift valves, and so forth used for shift control in the drive and reverse shift ranges can be partially shared, allowing the structure of the control device to be simpler, and affording optimal shift control in each range.
To achieve the stated object, the shift control device for an automatic transmission pertaining to the present invention has a power transmission mechanism (such as a parallel shaft transmission TM in the embodiments) comprising a drive power transmission path for transmitting drive force, and a reverse power transmission path for transmitting reverse power; a drive friction engagement element (such as a LOW clutch 11 in the embodiments) for selecting the drive power transmission path and a reverse friction engagement element (such as a 4th clutch 14 in the embodiments) for selecting the reverse power transmission path; and a hydraulic control valve (such as a shift control valve CV in the embodiments) for controlling the supply of engagement control hydraulic pressure to the drive friction engagement element and the reverse friction engagement element. This hydraulic control valve has a main pressure supply source (such as a main regulator valve 50, oil line 100, etc., in the embodiments) for supplying the main pressure of the engagement control hydraulic pressure a manual valve (such as a manual valve 58 in the embodiments) that is switched according to shift lever operation, first and second main pressure oil lines (such as oil lines 151, 152, 155, etc., in the embodiments) disposed in parallel between the main pressure supply source and the manual valve, and a plurality of engagement element oil lines (such as oil lines 121, 122, 156, 130, 131, 132, 133, etc., in the embodiments) disposed between the manual valve and the drive and reverse friction engagement elements. Also, a linear solenoid valve (such as a first linear solenoid valve 86, that is, linear A, in the embodiments) that allows the main pressure to be set as desired is provided to at least one of the first and second main pressure oil lines.
With a shift control device for an automatic transmission structured such as this, the engagement control hydraulic pressure from the first and second main pressure oil lines can be selectively supplied to the drive friction engagement element or the reverse friction engagement element on the basis of the operation of the manual valve. Specifically, the first and second main pressure oil lines can be used for both drive and reverse control, so fewer parts are needed for the shift control device, and control is simpler.
Accordingly, it is preferable if the above-mentioned first and second main pressure oil lines are linked to the drive friction engagement element when the manual valve is in the drive position, and are linked to the reverse friction engagement element when the manual valve is in the reverse position.
With the present invention, if the first and second main pressure oil lines are used selectively, it is possible, for example, to control the start of engagement by precisely controlling the engagement hydraulic pressure using a main pressure oil line having a linear solenoid valve, and upon completion of the engagement start control, to supply the line pressure directly using another main pressure oil line, so that the friction engagement element is securely engaged. As a result, the linear solenoid valve is controlled at a lower pressure, and the structure thereof can be simpler. Furthermore, even if there is a malfunction of the linear solenoid valve, the friction engagement element can still be engaged by using the other main pressure oil line, so reliability is better.
It is also preferable if a mechanical clutch mechanism (such as a dog-tooth clutch 16 in the embodiments) for mechanically switching the drive power transmission path and the reverse power transmission path, and a drive/reverse selection hydraulic servo mechanism (such as a drive/reverse selection hydraulic servo mechanism 70 in the embodiments) that hydraulically controls the operation of this mechanical clutch mechanism, are provided, and if the drive/reverse selection hydraulic servo mechanism is disposed within the hydraulic control valve, and the reverse engagement element oil line that connects the reverse friction engagement element to the manual valve is formed through the drive/ reverse selection hydraulic servo mechanism operating on the reverse side. This keeps the reverse friction engagement element from being engaged unless the drive/reverse selection hydraulic servo mechanism is switched to the reverse side, which improves reliability.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.